*{
  margin: 0;
  padding: 0;
  box-sizing: border-box;  
}

section{
  position: relative;

  /* 2. 将文字水平垂直居中： */
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;

  background: url(https://p9-juejin.byteimg.com/tos-cn-i-k3u1fbpfcp/de4571ba3e134425b3905b8e505493ed~tplv-k3u1fbpfcp-jj-mark:0:0:0:0:q75.image#?w=1920&h=1080&s=341630&e=jpg&b=6a7d95);
  background-position: center;
  background-attachment: fixed;
  background-size: cover;
  overflow: hidden;
}

section h2{
  font-size: 5em;
  color: #fff;
  pointer-events: none;

  /* 3. 这里以 "text" 开头 ->设置的是 "文字阴影" */
  text-shadow: 0 10px 20px rgba(0, 0, 0,0.5);
}

section .glass{
  /* 4. 因为又是某个特别的盒子在：当前主盒子上方进行效果显示 */
  /* 因此, 让人想到是否是 ->通过{定位}在[主盒子]上的... */
  position: absolute;
  transform: translate(-50%,-50%);
  pointer-events: none;
  width: 300px;
  height: 200px;
  box-shadow: 0 25px 50px rgba(0, 0, 0, 0.2);
  background: transparent;

  /* 4. 加上 "毛玻璃" 效果属性： */
  backdrop-filter: blur(10px);
  transition: 0.2s;
}